1. Field of the Invention
The present invention relates generally to fluid delivery devices. More particularly, the invention concerns an improved apparatus for infusing medicinal agents into an ambulatory patient at specific rates over extended periods of time.
2. Discussion of the Invention
The oral route is the most frequent route of drug administration. Oral administration is relatively easy for most patients and rarely causes physical discomfort. However, many medicinal agents require a parenteral route of administration thus bypassing the digestive system and precluding degradation by the catalytic enzymes in the digestive tract and the liver. The use of more potent medications at elevated concentrations has also increased the need for accuracy in controlling the delivery of such drugs. The delivery device, while not an active pharmacologic agent, may enhance the activity of the drug my mediating its therapeutic effectiveness. Certain classes of new pharmacologic agents possess a very narrow range of therapeutic effectiveness, for instance, too small a dose results in no effect, while too great a dose results in toxic reaction.
In the past, prolonged infusion of fluids has generally been accomplished using gravity flow means coupled with electronic based controls and typically involve the use of intravenous administration sets and the familiar bottle or solution bag suspended above the patient. Such methods are cumbersome, imprecise and, generally non-ambulatory requiring bed confinement of the patient. Periodic monitoring of the apparatus by the nurse or doctor is required to detect malfunctions of the infusion apparatus.
Devices of the character from which liquid is expelled from a relatively thick-walled bladder by internal stresses within the distended bladder have also been suggested for infusion of medicaments. For example, such bladder, or "balloon" type devices, are described in U.S. Pat. No. 3,469,578, issued to Bierman and in U.S. Pat. No. 4,318,400, issued to Perry.
A family of highly unique fluid delivery devices has been developed by the present inventor. These novel devices make use of recently developed elastomeric films, expandable foams and similar materials, which, in cooperation with a base define a fluid chamber that contains the fluid to be dispensed. The elastomeric film membrane or the expandable member controllably forces fluid within the chamber into outlet fluid flow channels provided in the device. Elastomeric film membrane devices are described in detail in U.S. Pat. No. 5,205,820 issued to the present inventor. U.S. Pat. No. 5,468,226, also issued to the present inventor, describes various types of expandable cellular elastomers and elastomeric foams used as the energy source of the fluid delivery device for expelling fluid from various physical forms of the fluid delivery device. Because of the pertinence of U.S. Pat. Nos. 5,205,820 and 5,468,226, these patents are hereby incorporated herein by reference in their entirety as though fully set forth herein. Co-pending U.S. application Ser. No. 08/541,030, filed Oct. 11, 1996 in which the present inventor is named as co-inventor, is also pertinent to one form of the apparatus of the invention which is described hereinafter. Accordingly, Ser. No. 08/541,030 is also hereby incorporated by reference as though fully set forth herein
The apparatus of the present invention, which takes various physical forms, makes use of a novel temperature expansive material as an energy source. This family of devices can also be used with minimal professional assistance in an alternate health care environment, such as the home. By way of example, devices of the invention can be comfortably and conveniently removably affixed to the patient's body and can be used with or without remotely located infusion sets for the continuous infusion of antibiotics, hormones, steroids, blood clotting agents, analgesics, and like medicinal agents. Similarly, the devices can be used for I-V chemotherapy and can accurately deliver fluids to the patient in precisely the correct quantities and at extended microfusion rates over time.
One of the embodiments of the present invention comprises an ambulatory fluid dispensing system which includes a relatively thin body attached rigid base assembly and a uniquely designed stored energy means which cooperates with the base assembly for controllably expelling fluid from the reservoir of the device. In this form of the invention, the stored energy means is provided in the form of a heat expandable gel, the nature of which will be described in greater detail hereinafter. In this particular form of the invention, a novel, remotely located subcutaneous infusion set can be quickly coupled to the base assembly to enable precise infusion of fluid to a patient upon an increase in temperature of the expandable gel caused by the normal body temperature of the patient. Alternatively, in other embodiments of the invention, infusion is accomplished by infusion means integrally formed with the base assembly.
In still other embodiments of the invention which also use a heat expandable gel as an energy source, medicinal fluids are delivered to the patient from the fluid dispenser via various types of infusion means. By way of example, such dispensers can accomplish parenteral administration of a beneficial agent by the subcutaneous, subdermal, intradermal, intramuscular or intravenous routes. Subcutaneous injection places the drug into the tissues between the skin and the muscle. Drugs administered in this manner are absorbed somewhat slowly. When the beneficial agent is administered subcutaneously, the needle can be inserted at a 45 degree angle or, in some cases, as with obese patients, at a 90 degree angle. A beneficial agent administered by the intravenous route is given directly into the blood by a needle inserted into a vein. In such instances, action occurs almost immediately. An intramuscular injection is the administration of a beneficial agent into a muscle. Agents given by this route are absorbed more rapidly than those given by the subcutaneous route. In addition, a larger volume (1-5 mL) can be given at one site. The sites for intramuscular administration are the deltoid muscle (upper arm), the ventrogluteal or dorsogluteal sites (hip), and the vastus lateralis (thigh). When giving a beneficial drug by the intramuscular route, the needle of the infusion means is preferably inserted at a 90 degree angle.
The primary thrust of the various inventions described herein is to provide novel fluid delivery systems which are compact, easy to use, relatively low profile and are eminently capable of meeting even the most stringent of fluid delivery tolerance requirements. In this regard, medical and pharmacological research continues to reveal the importance of the manner in which a medicinal agent is administered. For example, certain classes of pharmacological agents possess a very narrow dosage range of therapeutic effectiveness, in which case too small a dose will have no effect, while too great a dose can result in toxic reaction. In other instances, some forms of medication require an extended delivery time to achieve the utmost effectiveness of a medicinal therapeutic regimen.